This invention relates to an improved dual wheel assembly. In particular, the invention is directed to an improved dual wheel assembly for heavy transport vehicles, which permits the inner tire of the dual wheel to be removed and re-fitted without removing the outer wheel rim.
Dual wheels are commonly used in heavy transport vehicles, such as mining and earthmoving vehicles, to provide greater load bearing capacity and traction. A typical dual wheel assembly comprises a pair of juxtaposed wheel rims mounted coaxially on a common hub, with each rim having a tire fitted thereon.
The wheel rims are of substantially identical size and design. The tires are of the same, size and may be fitted interchangeably to either rim. Each wheel rim has a fixed annular flange at one end thereof which extends radially outwardly from the wheel rim and provides an end stop for the tire. The wheel rims are normally mounted to the hub with reversed orientations. That is, the end flange on the inner wheel is located at the inner end of the wheel rim, while the end flange on the outer wheel is located at the outer end of the outer wheel rim.
Due to the design and mounting of the wheels, and in particular the end flange on the outer wheel rim, the outer wheel must be removed from the hub in order to change the outer tire. Moreover, the outer wheel must also be removed in order to change the inner tire. Removing the wheel requires a large number of wheel nuts to be removed. This is a tedious and time consuming process, resulting in lengthy and costly downtime for the heavy duty vehicles. Specialised lifting equipment is also required for handling the heavy wheel rims. When the wheel is refitted, the wheel nuts must be screwed to the proper torque to avoid damage to the mounting knaves on the wheel.
It is an object of this invention to provide an improved dual wheel assembly which overcomes, or at least ameliorates, one or both of the abovedescribed disadvantages.
In one form, the invention comprises a dual wheel assembly for a vehicle, including
an inner wheel having an inner wheel rim and an inner tire mounted thereon,
an outer wheel having an outer wheel rim and an outer tire mounted thereon,
the inner and outer wheel rims being mounted coaxially on the vehicle, and the inner and the outer tires being substantially of the same size, characterised in that the outer wheel rim is of smaller diameter than the inner wheel rim such that the inner tire may pass around the outer wheel rim to enable it to be removed from the vehicle without removing the outer wheel rim.
Since it is not necessary to remove the outer wheel rim in order to enable the inner tire to be removed from the vehicle, the down time normally required for changing the inner tire is greatly reduced.
Each wheel has at least one removable annular bead seat located between the wheel rim and the respective tire, the bead seat(s) on the outer wheel having a greater radial thickness than the bead seats on the inner wheel to compensate for the reduced diameter of the outer wheel rim.
Preferably, the outer wheel has two removable bead seats located at respective opposite ends of the wheel rim. The inner removable bead seat abuts against a fixed annular flange on the wheel rim, either directly or indirectly. The outer removable bead seat is retained on the wheel rim in use by a locking ring on the outside thereof.
In another form, the invention can be broadly described as a wheel assembly comprising
a wheel rim,
a pair of removable annular bead seats mounted on the wheel rim, each bead seat being adapted to provide a seat for a respective bead of a tire,
characterised in that the wheel rim is of smaller diameter than a standard wheel rim for the tire and the bead seats are radially thicker than a standard bead seat, to thereby permit the tire to be fitted to the wheel rim.
In yet another form, the invention can be broadly described as a multiple wheel assembly comprising
a first wheel having a first wheel rim and a first tire fitted thereon,
a second wheel having a second wheel rim and a second tire fitted thereon,
the first and second wheel rims being mounted coaxially on a hub,
the first and second tires being of the same size and having inner and outer beads with predetermined inside diameters,
characterised in that the second wheel rim has a maximum outer diameter less than the inside bead diameter of the first wheel.
In order that the invention may be more fully understood and put into practice, but without limiting the scope of the invention, a preferred embodiment thereof will now be described with reference to the accompanying drawings.